Rheostat for electric-arc lamps.



PATENTED JAN. 3, 1905,

B. A. STOWE. RHEOSTAT FOR ELECTRIC ARC LAMPS.

APPLICATION FILED OUT. 28. 1903.

2 SHEETii-SHEET l.

PATENTBD JAN. 3, 1905.

B. A. STOWE.

RHEOSTAT FOR ELECTRIC ARC LAMPS.

APPLIUATION FILED OCT. 28. 1903.

2 SHEETS-SHEET 2.,

/ N VE N TOR At/orney C UNITED STATES BERNARD A. STOWE, OF CLEVELAND,OHIO, ASSIGNOR TO THE JANDUS Patented January 3, 1905.

PATENT OFFICE.

ELECTRIC CO., OF CLEVELAND, OHIO.

RHEOSTAT FOR ELECTRIC-ARC LAMPS.

SPECIFICATION forming part of Letters Patent No. 778,913, dated January3, 1905.

I Application filed October 28, 1903. Serial No. 178,926.

To a whom it may concern:

Be it known that I, BERNARD A. STowE, a resident of Cleveland, in thecounty of Cuyahoga and State of Ohio, have invented certain new anduseful Improvements in Rheostats for Electric-Arc Lamps; and I do herebydeclare the following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which itappertains to make and use the same.

My invention relates to improvements in electric-arc lamps, and moreparticularly to the construction and arrangement of the resistancedevice and its support, one object of the invention being to soconstruct the same as to permit of its ready insertion into and removalfrom the lamp structure without altering or removing any part of thelatter.

A further object is to so construct a resistance-coil as to minimize theextent of bearing-surface thereof against its support to facilitateventilation of the coil.

A further object is to so construct a resistance-coil and its support asto insure adequate ventilation of the coil.

With these objects in view the invention consists in certain novelfeatures of construction and combinations and arrangements of parts, ashereinafter set forth, and pointed out in the claims.

In the accompanying drawings, Figure 1 is a sectional View of a lampframe and easing, showing my improvements therein. Figs. 2, 3, and 4 areenlarged detail views.

The main shell orbody 1 of the lamp-casing consists of a single piece ofsheet metal, which is corrugated between special corrugatingrolls, saidcorrugations being confined to the intermediate portion of the sheet.The operation of corrugating in this manner results in producing acylindrical shell, inasmuch as the corrugations do. not extend the fullwidth of the plate. The metal in the intermediate portion of the plateis crimped and the stock gathered, so as to cause the sheet to assume acylindrical shape, the length of the uncorrugated portions determiningthe circumference of the enlarged portions of the shell and the depth ofthe corrugations determining the circumference,and consequently thediameter, of the corrugated or intermediate portion of the shell. Thedepths of the corrugations are graduated at the ends of the maincorrugations, so as to produce a gradual change in the diameterintermediate between the small and large diameters of the shell. Theenlarged lower portion of the shell is subsequently crimped, so as todecrease the diameter at the lower end of the edge of the shell,producing thereby a turning in of the shell which is utilized in thecompleted casings as a shield or screen 2 for preventing the ingress ofwater through the ventilating-holes 3 in a cast-iron ring 4, whichconstitutes an important member of the casing. The overlapping edges ofthe cylindrical shell are then secured by rivets, soldered or otherwise,and annular grooves or corrugations 5, rolled in the enlarged upperportion of the casing for the purpose of strengthening the same. A capor hood 6 is disposed over the upper enlarged end of the shell andprovided with aperipheral flange 7, preferably curved transversely. Thiscurved flange projects outwardly from the shell and acts as a watershedand also to preclude an entrance of dust, rain, and dirt into the casingthrough the ventilating-holes 8. The lower enlarged portion of thecasing is provided with an annular groove 9, which engages the cast-ironring at and secured thereto by warping the shell to said cast-iron ringjust previous to riveting or soldering the shell. The cast-iron ring atis provided with ventilating-holes 10 and supports from its innerperiphery a plain cylindrical shell 11. The method of securing the shell11 to the cast-iron ring is as follows:

The shell 11 primarily is rolled into cylindrical shape and the edgessecured by the well-known form of lock-seam. An annular bead 12 is thenrolled on the shell at a distance from the upper edge greater than thethickness of the cast-iron ring. The shell is then inserted into thering, seated against the annular head 12, and the stock projecting abovethe cast-iron ring swaged or turned over, and the two parts therebysecured together. The shell 11 has secured to its lower end, by means ofrivets or otherwise, a shallow stamping 13, of sheet metal, to which theouter globe-supporting device 1 1 is attached.

The floor-plate 15 of the lamp (which is supported by the central tube16 of the lamp) is provided with an annular raised portion 17 integraltherewith and presenting an inclined surface facing outwardly and whichconstitutes a surface of revolution of a truncated cone. Two bosses 18are provided at diametrically opposite points and project from the uppersurface of the iron ring l. These bosses are drilled and threadedradially and carry two screws 19, which project radially through andfrom the casing. The outer ends of these screws are provided withroughened heads 20 for convenience in operating the same. The screws 19are located in such position relative to the case that when the latteris raised to its normal seat within the lamp-hood 6 they will be in suchposition as to engage the inclined surface forming a part of thefloor-plate and which when screwed in results in forcing the caseupwardly with considerable pressure against its seat in the hood, andthus preventing relative movement between the casing and the parts ofthe lamp structure with which it may be in contact. it is simplynecessary to unscrew the two screws a suflicient distance to permittheir ends to disengage the inclined surface and the projecting ledge ofthe floor-plate casting. A block 21 is located within and secured to thehood, and the central portion of this block is provided with aninternally-threaded enlargement for the reception of the threaded upperend of carbon tube 16. This tube constitutes the spine of thelamp-frame, and around its upper portion the resistance-wire 22 and itssupport 23 are located.

The frame or support23 for the resistancecoil consists of a series ofinternally-grooved segments of porcelain, which when assembled make acomplete ring having a series of circumferential grooves 24: for thereception of the resistance-coil. Each segment is made with slots in thebases of the grooves for ventilating purposes, and the structure of eachsegment is strengthened by integral cross-bars 25. The ridges betweenthe grooves are notched, as at 26, to permit the resistance-coil to passfrom one groove to another, and suitable provision is also made (such asperforated seats 27) for the attachment of binding-posts. The

To remove the casing,

resistance-coil is so constructed as to minimize the extent of itscontact with the support, so as to insure the greatest possible facilityfor ventilation. The resistance-coil is therefore formed irregularly, soas to present the appearance of a spiral groove 28, extending from endto end thereof, said groove forming a continuous air-duct and permittingthe coil to bear only at intervals against the segmental support. Thesegmental porcelain support for the resistance-coil is located in theenlarged upper portion of the shell or casing, and each segment isdisposed upon a plate 29, and said plates are secured in turn to thehood 6 by means of bolts 30. By removing these bolts the segmentalsupport will be released, and then by removing the resistance-coil thesegments can be separated and removed from the lamp without disturbingthe backbone or carbon-tube 16 or any part of the lamp structure.

Having fully described my invention, what I claim as new, and desire tosecure by Letters Patent, is

1. The combination of a support consisting of several removable segmentshaving alining grooves, and a resistance mounted removably in saidgrooves.

2. A resistance device comprising a sectional, annular support ofinsulating material having a groove therein, and a coil ofresistanee-wire removably mounted in said groove, said coil havingdepressions to reduce the contacting portions of the coil with thesupport.

8. A resistance device, comprising a segmental support consisting ofsegments of insulating material cooperating to form a ring havingperipheral grooves, and a coil of resistance-wire mounted in saidgrooves.

4. A resistance device comprising several separable porcelain segmentscooperating to form a ring, said segments having alining grooves andhaving slots in the bottoms of said grooves, a resistance-coil wound onthe porcelain ring, and means for holding the latter in position in alamp.

In testimony whereof I have signed this specification in the presence oftwo subscribing witnesses.

BERNARD A. STOWE.

Vitnesses:

JOHN J. ANGEL, HENRY J. Voer

